Display device and method of manufacturing the same

ABSTRACT

A display device and manufacturing method thereof with a high level of reliability is provided without increasing the number of manufacturing processes. The display device includes a first conductor, a first insulation layer including a first contact hole exposing a part of the first conductor, a second insulation layer including a second contact hole exposing at least a part of the first contact hole and a part of a surface of the first insulation layer, a pixel electrode overlapping a part of the second contact hole and electrically connected to the first conductor, and a third insulation layer contacting the first insulation layer via the second contact hole.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2015-087356, filed on Apr. 22,2015, the entire contents of which are incorporated herein by reference.

FIELD

The present invention is related to a display device including aplurality of pixels. In particular, the present invention is related toa display device arranged with a light emitting element including anorganic light emitting layer in each pixel.

BACKGROUND

Conventionally, a display device is known including a plurality ofpixels formed above a substrate. A LCD (Liquid Crystal Display) and OLED(Organic Light Emitting Diode) display are typical examples of such adisplay device. In particular, in recent years, the development of OLEDdisplays having excellent response characteristics and viewing anglecharacteristics is progressing rapidly.

An OLED display is a display device with a light emitting element usingan electroluminescence phenomenon arranged in each pixel. A displaydevice using an organic light emitting layer as a light emitting elementis called an organic EL (Electro Luminescence) display device. This typeof display device can emit light in at colors of various wavelengths byselecting the light emitting material which forms the light emittinglayer.

Generally, each pixel formed above a substrate includes a light emittingelement and a drive transistor which supplies a current for driving thelight emitting element. After a drive transistor is formed above thesubstrate, the drive transistor is covered by an insulation layer formedfrom an organic resin material and a light emitting element is formedabove the insulation layer. The insulation layer is used as a planarizedfilm for relieving undulations caused by the transistor. For example, adisplay device having the structure described in Japanese Laid OpenPatent No. 2014-142641 is typically known.

SUMMARY

A display device in one embodiment of the present invention includes afirst conductor, a first insulation layer including a first contact holeexposing a part of the first conductor, a second insulation layerincluding a second contact hole exposing at least a part of the firstcontact hole and a part of a surface of the first insulation layer, apixel electrode overlapping a part of the second contact hole andelectrically connected to the first conductor, and a third insulationlayer contacting the first insulation layer via the second contact hole.The pixel electrode may also be electrically connected to the firstconductor via a second conductor contacting the first conductor.

A method of manufacturing a display device in one embodiment of thepresent invention includes forming a first conductor, forming a firstinsulation layer arranged with a first contact hole so as to expose apart of the first conductor, forming a second insulation layer arrangedwith a second contact hole so as to expose at least a part of the firstcontact hole and a part of a surface of the first insulation layer,forming a pixel electrode overlapping a part of the second contact holeand electrically connected to the first conductor, and forming a thirdinsulation layer contacting the first insulation layer via the secondcontact hole. Furthermore, a second conductor may be formed electricallyconnected to the first conductor so as to cover the entire first contacthole after forming the first contact hole, and the pixel electrode maybe electrically connected to the first conductor via the secondconductor.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a diagram showing a structure of an organic EL display deviceof a first embodiment;

FIG. 2 is a diagram showing a structure of a pixel part of an organic ELdisplay device of a first embodiment;

FIG. 3 is a diagram showing a structure of pixel of an organic ELdisplay device of a first embodiment;

FIG. 4 is a diagram showing a structure of one part of a pixel of anorganic EL display device of a first embodiment;

FIG. 5A is a diagram showing a structure of one part of a pixel of anorganic EL display device as a comparative example;

FIG. 5B is a diagram showing a structure of one part of a pixel of anorganic EL display device of a first embodiment;

FIG. 5C is a diagram showing a structure of one part of a pixel of anorganic EL display device as a comparative example;

FIG. 6A is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a first embodiment;

FIG. 6B is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a first embodiment;

FIG. 7A is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a first embodiment;

FIG. 7B is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a first embodiment;

FIG. 8 is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a first embodiment;

FIG. 9 is a diagram showing a structure of a pixel of an organic ELdisplay device of a second embodiment;

FIG. 10 is a diagram showing a structure of one part of a pixel of anorganic EL display device of a second embodiment;

FIG. 11 is a diagram showing a structure of a pixel of an organic ELdisplay device of a third embodiment;

FIG. 12A is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a third embodiment;

FIG. 12B is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a third embodiment;

FIG. 13A is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a third embodiment; and

FIG. 13B is a diagram showing a manufacturing process of an arraysubstrate of an organic EL display device of a third embodiment.

DESCRIPTION OF EMBODIMENTS

For example, the display device described in FIG. 22 of patent document1 is arranged with a resin layer 7017 as a planarized film above a drivetransistor 7001. A contact hole which reaches an electrode forming apart of the drive transistor 7001 is arranged in the resin layer 7017.In addition, a second protection insulation layer 7018 formed fromsilicon nitride is arranged so as to cover the entire resin layer 7017including the contact hole. In other words, the resin layer 7017 is in asealed state due to the second protection insulation layer 7018.

From the experience of the present inventors, it is known that in amanufacturing process after forming a resin layer as a planarized film,gas including water from the resin layer is sometimes produced due toheating and the like. As a result, in the case were the structuredescribed in the patent document 1 is adopted, there is nowhere for gasproduced from a resin layer to escape, water accumulates the boundarybetween the resin layer and a protection layer above and there is adanger that protection layer may peel away. This type of problem leadsto the effect of reducing the reliability of the display device.

One aim of the invention is to provide a display device with a level ofreliability and a manufacturing method thereof without increasing thenumber of manufacturing processes.

Each embodiment of the present invention is explained below whilereferring to the diagrams. However, the present invention can berealized by various different forms without departing from the scope ofthe present invention and should not be interpreted as being limited tothe contents described in the embodiments exemplified below.

In addition, although the width, thickness and shape of each componentare represented schematically compared to actual component in order tobetter clarify the explanation of the invention, these are merelyexamples and should not limit an interpretation of the presentinvention. In addition, in the present specification and each diagram,the same reference symbols are attached to the same elements which havebeen previously been described and therefore a detailed explanation ofsuch elements may be omitted.

First Embodiment

<Structure of a Display Device>

FIG. 1 is a diagram showing a structure of an organic EL display device100 in a first embodiment. Specifically, FIG. 1 shows an approximatestructure in the case where the EL display device 100 is seen in aplanar view. Furthermore, the appearance of an EL display device seenfrom a perpendicular direction to the screen (display region) isreferred to as [planar view] in the present specification. As is shownin FIG. 1, the EL display device 100 is arranged with a pixel part(display region) 102, a scanning line drive circuit 103, a data linedrive circuit 104 and a driver IC 105 formed above a substrate 101. Thedriver circuit 105 functions as a control part for providing signals tothe scanning line drive circuit 103 and date line drive circuit 104.

Furthermore, the data line drive circuit 104 may sometimes be includedin the driver IC 105. Although an example in which the driver IC 105 isintegrally formed above the substrate 101 is shown in FIG. 1, the driverIC 105 may also be arranged above a separate substrate 101 in a formsuch as a IC chip. In addition, an externally attached form may also beadopted in which the driver IC 105 is arranged on a FPC (FlexiblePrinted Circuits).

A plurality of pixels 201 are arranged in matrix shape in a rowdirection and column direction in the pixel part 102 shown in FIG. 102.A data signal is provided from the data line drive circuit 104 accordingto image data in each pixel 201. A transistor arranged within each pixel201 is driven according to these data signals and it screen display ispossible according to the image data. Typically, it is possible to use athin film transistor as the transistor. However, an element may be usedas long as it is arranged with a current control function. In addition,a thin film transistor may be an N channel type or P channel typetransistor. In the present embodiment, the thin film transistor used inthe display part 102 is an N channel type.

FIG. 2 is a diagram showing a structure of the pixel part 102 in theorganic EL display device 100 of the first embodiment. Specifically, apart of the pixel part 102 is shown having a structure of four pixels201 seen in a planar view. Furthermore, although four pixels areexemplified in FIG. 2, actually millions of pixels 201 are arranged in amatrix shape. In addition, the structure within the pixel 201 is notlimited to the structure shown in FIG. 2.

The interior of the pixel 201 includes a thin film transistor 202. As isdescribed herein, the thin film transistor 202 functions as a currentcontrol element for supplying an appropriate current to a light emittingelement. That is, a pixel electrode 202 is electrically connected to asource electrode or drain electrode of the thin film transistor 202 anda current is supplied to a light emitting element in which the pixelelectrode 203 is the anode. Furthermore, although an explanation isomitted here, a thin film transistor which functions as a switchingelement may be arranged within the pixel 201 and a pixel may be formedusing a plurality of transistors.

The organic EL display device 100 of the present embodiment is arrangedwith an aperture part 204 for removing water adjacent to the pixelelectrode 203. The aperture part 204 is arranged in an inorganicinsulation layer which covers a resin layer for emitting gas whichincludes water produced from the resin layer which functions as aplanarized film to the exterior. A specifically structure is describedherein.

Furthermore, although it is exemplified of the pixels 201 arranged instripes as one example of the arrangement of the pixels 201 in thepresent embodiment, an arrangement which realizes a delta arrangement,Bayer arrangement or pentile structure are also possible.

FIG. 3 is a diagram showing the structure of a pixel 201 in the organicEL display device 100 of the first embodiment. Specifically, FIG. 3shows a cross-section structure where the pixel 201 shown in FIG. 2 iscut along the line III-III′. In FIG. 3, an insulation layer formed froman inorganic material such as silicon oxide, silicon nitride or aluminumoxide is arranged as a ground layer 302 above a first substrate 301 andabove this the thin film transistor 202 is formed. For example, it ispossible to adopt a stacked structure of a silicon oxide layer andsilicon nitride layer as the ground layer 302. This structure may beappropriately determined after considering adhesion with the firstsubstrate 301 or gas barrier properties with respect to the thin filmtransistor 202.

It is possible to use a glass substrate, silica substrate or flexiblesubstrate (polyimide, polyethylene terephthalate, polyethylenenaphthalate or a substrate which can be bent) as the first substrate301. In the case where the first substrate 301 does not require lightblocking properties, it is possible to use a metal substrate, ceramicsubstrate or semiconductor substrate. In particular, in the case where aflexible substrate is used as the substrate, it is preferred that aground layer including the stacked structure described above is arrangedin order to increase the protection function from the exterior.

The thin film transistor 202 may be formed using any method. Thestructure of the thin film transistor 202 may be a top gate type orbottom gate type. In the present embodiment, the thin film transistor202 includes a semiconductor layer 303 arranged above the ground layer302, a gate insulation film 304 covering the semiconductor layer 304, agate electrode 305 arranged above the gate insulation film 304, aninterlayer insulation film 306 covering the gate electrode 305, and asource electrode 307 and drain electrode 307 arranged above theinterlayer insulation film 306 and each connected to the semiconductorlayer 303 respectively.

Furthermore, there is no particular limitation to the material of eachlayer forming the thin film transistor 202. Typically it is possible touse polysilicon or amorphous silicon as the semiconductor layer 303 forexample. It is possible to use silicon oxide as the gate insulation film304. It is possible to use silicon oxide or silicon nitride as theinterlayer insulation film 306 and these layers can be stacked.

A first insulation layer 309 which functions as a planarized film isarranged above the thin film transistor 202 formed as described above.In the present embodiment, a thin film formed by a resin material isused as the first insulation layer 309. For example, it is possible touse an organic resin material such as polyimide, polyamide, acryl orepoxy. These materials can be used to form a film using a solutioncoating method and have characteristics such as high planarizationeffects.

The first insulation layer 309 includes a first contact hole 310 whichexposes a part of the source electrode or drain electrode 308 (that is,overlaps a part of the source electrode or drain electrode 308). Here,the positional relationship between the drain electrode 308 and thefirst contact hole 310 is explained using FIG. 4. FIG. 4 is a diagramshowing the structure of a part of the pixel 201 in the organic ELdisplay device 100 of the first embodiment. Specifically, FIG. 4 showsan exploded view of the vicinity of the aperture part 204 in FIG. 2 seenfrom a planar view.

The first contact hole 310 is an aperture part for electricallyconnecting a pixel electrode 313 described herein and the sourceelectrode or drain electrode 308. Therefore, as is shown in FIG. 4, thefirst contact hole 310 is arranged on the interior side of the externalshape of the source electrode or drain electrode 308, and the sourceelectrode or drain electrode 308 become exposed at the bottom surface ofthe first contact hole 310 at the point when the first contact hole 310is formed.

Furthermore, a source electrode or drain electrode in the presentembodiment correspond to [first conductor] in the scope of the patentclaims. However, [first conductor] is not limited to a source electrodeor drain electrode and may be any conductor electrically connected to apixel electrode.

A second insulation layer 311 which functions as a protection layer isarranged above the first insulation layer 309. In the presentembodiment, a thin film formed from an inorganic material is used as thesecond insulation layer 311. For example, it is possible to an inorganicmaterial such as silicon oxide, silicon nitride or silicon oxynitride.In particular, a silicon nitride film is useful as a protection layersince it has excellent gas barrier properties.

The second insulation layer 311 includes a second contact hole 312 whichoverlaps a part of the first contact hole 310 and a part of the surfaceof the first insulation layer 309. As is shown in FIG. 3 and FIG. 4, thesecond contact hole 312 overlaps a part of the first contact hole 310and thereby exposes a part of the source electrode or drain electrode308. In addition, since a part of the surface of the first insulationlayer 309 is also overlapped, a part of the surface of the firstinsulation layer 309 is also exposed. As a result, the second contacthole 312 in the present embodiment is arranged astride from the interiorof the first contact hole 310 above the surface of the first insulationlayer 309.

The pixel electrode 313 overlaps a part of the second contact hole 312and is arranged so as to be electrically connected with the sourceelectrode or drain electrode 308. Since the pixel electrode 313 in thecase of the present embodiment overlaps a part of the second contacthole 312, a part of the surface of the first insulation layer 309remains exposed at a part which is not overlapped. The part of the firstinsulation layer 309 which is exposed (region 204 shown by the diagonalline in FIG. 4) corresponds to the aperture part 204 for removing watershown in FIG. 2.

In the organic EL display device 100 of the present embodiment, thepixel electrode 313 functions as an anode forming an organic EL element.The pixel electrode 313 is formed by either a top emission typestructure or bottom emission type structure. For example, in the case ofa top emission type structure, a metal film with a high reflectance isused as the pixel electrode 313 or a stacked structure of a high workfunction transparent conductive film such as an indium oxide transparentconductive film (ITO for example), or a zinc oxide transparentconductive film (IZO, ZnO for example) film and a metal film. Reversely,in the case of a bottom emission type structure, a transparentconductive film described above may be used as the pixel electrode 313.In the present embodiment, a top emission type organic EL display deviceis explained as an example.

A third insulation layer 314 formed from a resin material is arrangedbetween adjacent pixel electrodes 313. The third insulation layer 314includes an aperture part at a part which serves as a light emittingregion of a pixel. That is, the third insulation layer 314 is arrangedso as to cover the upper section of the thin film transistor 202 and anedge part of the pixel electrode 313. Since this type of thirdinsulation layer 314 functions as a component which sections each pixel,it is also generally referred to as a [separation wall] or [bank]. Theaperture part of the third insulation layer 314 is preferred to beformed so that the inner wall has a taper shape. When a light emittinglayer described herein is formed in this way, it is possible to reducecoverage defects in an end part of the pixel electrode 313.

Furthermore, the third insulation layer 314 does not cover an end partof the pixel electrode 313 but may be made to function as a fillermaterial which fills recessed parts caused by the first contact hole310. It is possible to use a resin material such as polyimide,polyamide, acryl, epoxy or siloxane group as the third insulation layer314.

Here, in the case where the structure of the present embodiment isadopted, the third insulation layer 314 contacts the first insulationlayer 309 via the aperture part 204 for removing water describedpreviously. Therefore, in a water extraction process (specifically,heating process) of the first insulation layer 309 after forming thethird insulation layer 314 (that is, before forming a light emittinglayer described herein), gas including water produced within the firstinsulation layer 309 escapes to the side of the third insulation layer314 via the aperture part 204 and is emitted to the exterior passingthrough the interior of the third insulation layer 314. That is, wateris not trapped within the third insulation layer 314 as in conventionaltechnology and it is possible to perform a water removal process evenafter the second insulation layer 311 is arranged as a protection layer.In this way, it is possible to realize a display device with a highlevel of reliability.

An electroluminescence layer (EL layer) 315 is arranged above the pixelelectrode 313 and third insulation layer 314. The EL layer 315 includesat least a light emitting layer formed from an organic material andfunctions as a light emitting part of an organic EL element. In additionto a light emitting layer, various types of charge transport layer suchas an electron injection layer, electron transport layer, hole injectionlayer and hole transport layer may also be included in the EL layer 315.

Furthermore, in the present embodiment, a structure is adopted in whichthe EL layer 315 which emits white light is arranged and each color RGBis displayed by passing through a color filter. However, it is possibleto use other structures and other materials in the EL layer 315 and thepresent invention is not particularly limited to the structure of thepresent embodiment. In addition, the EL layer 315 may also be formedonly above pixel electrode 313. That is, the EL layer 315 is not formedabove the third insulation layer 314 but may be coated for each pixel.For example, one pixel may be formed by three sub-pixels, an EL layercorresponding to each color R (red), G (green) and B (blue) may beformed in each of the three sub-pixels respectively, or one pixel may beformed by four sub-pixels, and an EL layer corresponding to each color R(red), G (green), B (blue) and white (W) may be formed in each of thefour sub-pixels respectively.

A common electrode 316 which functions as a cathode of an organic ELelement is arranged above the EL layer 315. Since the organic EL displaydevice 100 in the present embodiment is a top emission type, atransparent electrode is used as the common electrode 316. A MgAg thinfilm or transparent conductive film (ITO or IZO) is used as a thin filmfor forming a transparent electrode. The common electrode 316 isarranged on the entire surface of the pixel part 102 abridging eachpixel. In addition, the common electrode 316 is electrically connectedto an exterior terminal via a conductive layer on a lower layer in aperiphery region in the vicinity of the end part of the display part102.

In the present embodiment, an EL element is formed by the pixelelectrode 313, EL layer 315 and common electrode 316. Furthermore, afourth insulation layer 317 formed from an inorganic material isarranged to protect the EL element from external water and the like. Itis preferred that an inorganic insulation film with good compactnesssuch as a silicon nitride film is used as the fourth insulation layer317.

The first substrate 301 to the fourth insulation layer 317 explainedabove are collectively referred to as an array substrate in the presentembodiment.

An opposing substrate is arranged via a filler material 318 whichfunctions as an adhesive and a protection material above the arraysubstrate. It is possible to use polyimide, polyamide, acryl, epoxy orsiloxane group resin material as the filler material 318. A spacer maybe arranged in the filler material 318 for securing a gap between thearray substrate and opposing substrate. This type of spacer may be mixedinto the filler material or can be formed using a resin above the arraysubstrate. In addition, as long as it is possible to realize sufficientsealing at a substrate periphery part and maintain a gap between thearray substrate and opposing substrate, it is also possible seal onlythe substrate periphery part with the interior being hollow withoutusing the filler material 318. In addition, it is also possible to use alayer formed from polyimide, polyamide, acryl, epoxy or siloxane groupresin material as it is as a sealing layer without using the opposingsubstrate.

Furthermore, in the present embodiment, [opposing substrate] includes asecond substrate 319, a color filter 320 corresponding to each color RGBarranged on the main surface (surface facing the first substrate 301) ofthe second substrate 319 and black mask 321 arranged between the colorfilters. The black mask 321 can be formed using a metal material with arelatively lower reflectance than other metals such as titanium (Ti) orchrome (Cr), or a resin containing a black or equivalent pigment.

However, the structure of the opposing substrate is not limited to this.For example, an overcoat layer may be formed while planarizing afterarranging the color filter 320 and black mask 321. In addition, theblack mask 321 may be omitted and if the EL layer 316 is arrangedseparately for each pixel for each color RGBW, it is possible to omitthe color filter from the opposing substrate. Furthermore, if the colorfilter is omitted or formed on the first substrate 301 side, it is alsopossible to omit the opposing substrate itself.

In the organic EL display device 100 of the present embodiment formed asdescribed above, the second contact hole 312 arranged against the secondinsulation layer 311 functions both as an aperture part for electricallyconnecting a source electrode or drain electrode 308 with the pixelelectrode 313 and as an aperture part for removing water. In this way,it is possible to electrically connect the drain electrode 308 with thepixel electrode 313 just by arranging the second contact hole 312,discharge gas including water from a planarized film and also improvethe reliability of the organic EL display device.

Furthermore, although it is possible to separately arrange an aperturepart for exposing the source electrode or drain electrode and anaperture part for removing water, in the case, since it is necessary toobtain a design margin for each aperture part, there is a danger thatthe area for securing the aperture parts becomes very large as a whole.In the case of the present embodiment, since it is possible toelectrically connect a source electrode or drain electrode with a pixelelectrode and form an aperture part for removing water using a singleaperture part, there is the merit of having a compact structure comparedto the case of arranging separate aperture parts.

For example, FIG. 5A is a diagram showing an example (comparativeexample) in the case where an aperture part 401 for exposing a sourceelectrode or drain electrode and an aperture part 402 for removing waterare separately arranged. However, FIG. 5B is a diagram showing anexample (example 1) in the case where the aperture part 204 of thepresent embodiment is arranged and FIG. 5C is a diagram showing anotherexample (example 2) in the case where the aperture part 204 of thepresent embodiment is arranged.

In the case of FIG. 5A, it is necessary to secure a design margin inboth the aperture part 401 and aperture part 402 and integration at ahigh density is difficult. However, as is shown in FIG. 5B and FIG. 5C,the aperture part 204 according to the present embodiment can performboth electrical connection between a drain electrode and pixel electrodeand remove water using a single aperture part. As a result, for exampleif the pixel size is the same, it is possible to make the width (X′) ofthe light emitting region 404 in FIG. 5B larger than the width (X) ofthe light emitting region 403 in FIG. 5A. In this way, it is possible toincrease the aperture ratio of a pixel and contribute to an improvementin luminosity of a display device. In addition, for example if the widthof a light emitting region is the same, it is possible to make the pitch(Y′) of a pixel in FIG. 5C narrower than the pitch (Y) of a pixel inFIG. 5A. In this way, it is possible to increase the pixel layoutdensity and contribute to high definition of a display device.

The manufacturing process of the array substrate in the organic ELdisplay device 100 of the present embodiment arranged with the structuredescribed above is explained below while referring to FIG. 6A to FIG. 8.

<Manufacturing Method of a Display Device>

First, as is shown in FIGS. 6A and 6B, a ground layer 302 is formedabove the first substrate 301 and the thin film transistor (TFT) 202 isformed thereupon. It is possible to use a glass substrate, silicasubstrate or flexible substrate (polyimide, polyethylene terephthalate,polyethylene naphthalate or a substrate which can be bent) as the firstsubstrate 301. In the case where the first substrate 301 does notrequire light blocking properties, it is possible to use a metalsubstrate, ceramic substrate or semiconductor substrate.

Typically, it is possible to use an insulation layer formed from siliconoxide or silicon nitride or a stacked film of these as the ground layer302. The ground layer 302 has a function for preventing the infiltrationof contaminants from the first substrate 301 and relieving stressproduced by stretching of the first substrate 301.

The thin film transistor 202 may also be formed using any method asdescribed previously. For example, the semiconductor layer 303 is formedfrom silicon above the ground layer 302 and a gate insulation film 304is formed from silicon oxide so as to cover the semiconductor layer 303.A gate electrode 305 is formed from a metal material above the gateinsulation film 304 and an interlayer insulation film 306 is formed soas to cover the gate electrode 305. It is possible to use an insulationlayer formed from silicon oxide or silicon nitride or a stacked film ofthese as the interlayer insulation film 306. Furthermore, a sourceelectrode and drain electrode 307, 308 are formed from a metal materialafter forming a contact hole which contacts the semiconductor layer 303in the interlayer insulation film 306 and gate insulation film 304.

The thin film transistor 202 is formed using the processes describedabove. Furthermore, although an example is exemplified in the presentembodiment of forming a top gate type thin film transistor as the thinfilm transistor 202, a bottom gate type thin film transistor may also beused

After the thin film transistor 202 is formed, the first insulation layer309 is formed and the first contact hole 310 is formed contacting thesource electrode or drain electrode 308 as is shown in FIG. 6B. In thepresent embodiment, a resin layer is formed from a photosensitive acrylresin as the first insulation layer 309 and the first contact hole 310is formed by exposure using a photomask. Furthermore, the firstinsulation layer 309 is preferred to have a film thickness of 1˜3 μmsince it is used as a planarized film.

Next, as is shown in FIG. 7A, a second insulation layer 311 is formed soas to cover the first insulation layer 309 arranged with the firstcontact hole 310. Although a silicon nitride layer is used as the secondinsulation layer 311 in the present embodiment, a silicon oxide layermay also be used. The film thickness may be appropriately set within arange of 30˜300 nm considering barrier properties with respect to waterand the like. The second insulation layer 311 is patterned using a usualphotolithography process and is arranged with a second contact hole 312.As is shown in FIG. 4, the second contact hole 312 is arranged bridgingpart of the first contact hole 310 and a part of the first insulationlayer 309 in a rectangle shape.

When the second contact hole 312 is formed with respect to the secondinsulation layer 311, the pixel electrode 313 is formed as is shown inFIG. 7B. Furthermore, the pixel electrode 313 is formed corresponding tothe position of each of a plurality of pixels respectively. Furthermore,the pixel electrode 313 is formed so as to cover the entire firstcontact hole 310 and a part of the second contact hole 312.Specifically, in the case of the present embodiment, a three layerstructured conductive layer is formed sandwiching a silver thin filmsuch as an ITO thin film and this conductive layer is patterned to formthe pixel electrode 313. In the present embodiment, a silver thin filmis used as a reflective layer in order to adopt a structure in whichlight is extracted towards the upper part (upwards is defined as thedirection furthest from the first substrate 301) of the display device.The pixel electrode 313 formed in this way functions as an anode in anorganic EL display element of the present embodiment.

Next, a third insulation layer 314 which functions as a bank is formedas is shown in FIG. 8. The third insulation layer 314 can be obtained byforming an aperture part in a part corresponding to the light emittingregion of a pixel after forming a resin layer with film thickness ofabout 1 μm. That is, the third insulation layer 314 is formed so as tocover an upper part of the thin film transistor 202 and an edge part ofthe pixel electrode 313. As a result, a part of the third insulationlayer 314 contacts the first insulation layer 309 via a part of thesecond contact hole 312.

In the present embodiment, when the third insulation layer 314 isformed, a heating process is performed in order to remove water from thefirst insulation layer 309 and third insulation layer 314. However, thisprocess is not always required. Following this, an EL layer 315 isformed above the pixel electrode 313 and third insulation layer 314. Inthe present embodiment, a layer which emits white light is formedcommonly for all pixels as the EL layer 315. In this way, it is possibleto simplify the manufacturing process and construct a manufacturingprocess with a high productivity. Furthermore, in addition to a lightemitting layer, a charge injection layer, charge transport layer or bothmay also be included in the EL layer 315. In addition, it is possible toform the EL layer 315 using a known method. For example, the EL layer315 may be formed by forming a low molecular EL material using vapordeposition or by forming a high molecular EL material using an inkjetmethod or sputtering method and the like.

Next, a common electrode 313 which functions as a cathode of an organicEL element is formed. In the present embodiment, an ITO film or IZO filmformed by a sputtering method are used as the common electrode 316.Other transparent conductive films may also be used and a metal filmformed such as a MgAg film sufficiently thin to allow light to passthrough may also be used. Following this, a fourth insulation layer 317is formed from silicon nitride as a protection film. At this time, it isdesirable that the common electrode 316 and fourth insulation layer 317are formed consecutively so that they do not contact external air.

As described above, an array substrate of the organic EL display deviceof the present embodiment is complete. Furthermore, it is possible toobtain the organic EL display device 100 shown in FIG. 3 if the opposingsubstrate (substrate formed from the second substrate 319, color filter320 and black mask 321) is bonded with the completed array substrateusing the filler material 318.

Second Embodiment

FIG. 9 is a diagram showing a structure of a pixel 201 of an organic ELdisplay device 200 of the second embodiment. FIG. 10 is a diagramshowing a structure of a part of the pixel 201 of the organic EL displaydevice 200 of the second embodiment. The difference between the firstand second embodiments is that in the organic EL display device of thesecond embodiment, a second contact hole 401 is arranged so as tooverlap the entire range of the first contact hole 310. Since theremaining structure is the same as the organic EL display device 100 ofthe first embodiment, a detailed explanation is omitted.

In the structure shown in FIG. 3 in the first embodiment, an example isshown in which the second contact hole 312 arranged in the secondinsulation layer 311 overlaps a part of the first contact hole 310arranged in the first insulation layer 309. In the case of the presentembodiment, all of the second insulation layer 311 within the firstcontact hole 310 is removed as is shown in FIG. 9 and the second contacthole 401 overlaps the entire range of the first contact hole 310. Thatis, a region which serves as the second contact hole 401 encompasses aregion which serves as the first contact hole 310.

In addition, the first contact hole 310 is arranged on the inner side ofthe second contact hole 312 from the planar view diagram shown in FIG.10. As a result, a part of the source electrode or drain electrode 308arranged underneath is exposed in the entire region of the bottomsurface of the first contact hole 310.

As is clear from a comparison of FIG. 4 and FIG. 10, because the contactarea between the source electrode or drain electrode 308 and the pixelelectrode 313 increases in the case of the structure of the presentembodiment, it is possible to obtain a good electrical connectionbetween the two. Furthermore, the area of the aperture part 402 forremoving water increases as the area of the second contact hole 312increases, and the capability for discharging gas including water fromthe first insulation layer 309 is further improved.

As described above, the organic EL display device 200 of the presentembodiment has a better electrical connection between the drainelectrode 308 and pixel electrode 313 and better discharge capabilitiesof a gas including water from the first insulation layer 309 in additionto the effects explained with respect to the organic EL display device100 of the first embodiment.

Third Embodiment

FIG. 11 is a diagram showing a structure of a pixel 201 of an organic ELdisplay device 300 of the third embodiment. FIGS. 12A, 12B, 13A and 13Bare diagrams showing a manufacturing process of the organic EL displaydevice 300 of the third embodiment. The difference between the first andthird embodiments is that in the organic EL display device of the thirdembodiment, a second conductor is arranged so as to cover the firstcontact hole 310 and a capacitance electrode is arranged on the lowerpart of an organic EL element. Since the remaining structure is the sameas the organic EL display device 100 of the first embodiment, a detailedexplanation is omitted.

As is shown in FIG. 11, a second conductor 501 is arranged above thefirst contact hole 310 in the organic EL display device 300 of thepresent embodiment. The second conductor 501 functions as an electrodefor electrically connecting the source electrode or drain electrode 308with the pixel electrode 313. Although the second conductor 501 can beformed from various conductive materials, it is preferred to use amaterial which can secure a selection ratio at the time of etchingbetween a conductive material for forming the capacitance electrode 502described herein. In the present embodiment, it is possible to form thesecond conductor 501 using a transparent conductive material includingat least one selected from ITO IZO and ZnO. In this way, the secondconductor 501 can be made to function as an etching stopper when formingthe capacitance electrode 502.

Furthermore, a third conductor 502 is arranged between the pixelelectrode 313 and first insulation layer 309 in the organic EL displaydevice 300 of the present embodiment. The third conductor 502 functionsas a capacitance electrode in a pair with the pixel electrode 308. Thatis, since the second insulation layer 311 is arranged as a dielectricbetween the capacitance electrode 502 an pixel electrode 308, the thirdconductor 502 functions as one electrode of a capacitor connected to anEL element. Furthermore, the third conductor 502 may be electricallyconnected with a power supply wire or may be electrically connected withthe common electrode 316.

The third conductor 502 can be formed from various conductive materials.Although the third conductor 502 is formed from a stacked structuresandwiching a molybdenum (Mo) thin film and aluminum (Al) thin film inthe present embodiment, the third conductor 502 is not limited to thisstructure.

Next, a manufacturing process of the organic EL display device 300 ofthe third embodiment is explained. Furthermore, since the processes upto before forming the first contact hole 310 and the processes afterforming the pixel electrode 313 are the same as in the first embodiment,an explanation is omitted here.

After forming the first contact hole 310 using the same process as inthe first embodiment, in the present embodiment, a thin film is formedfrom ITO using a sputtering method as is shown in FIG. 12A, and theformed thin film is patterned to form the second conductor 501. At thistime, the shape of the second conductor 501 is formed so as to overlapthe entire range of the first contact hole 310 when viewing the organicEL display device 300 from above.

When the second conductor 501 is formed, the third conductor 502 isformed next as is shown in FIG. 12B. Specifically, a molybdenum thinfilm, aluminum thin film and molybdenum thin film are stacked in orderand then patterned to form the third conductor 502 so as to cover thesecond conductor 501 and first insulation layer 309. At this time, sincethere is a sufficient selection ratio between the second conductor 501and third conductor 502 with respect to an etchant used when etching thethird conductor 502, the second conductor 501 is not etched or removed.

Furthermore, in the case where the second conductor 501 is not arranged,the source electrode or drain electrode 308 formed from a metal materialincluding aluminum and the like exists below. Therefore, there is adanger that the source electrode or drain electrode 308 may also beetched when etching the third conductor 502. In the case of thestructure of the present embodiment, since the second conductor 501functions as an etchant stopper, etching is not performed as far as thesource electrode or drain electrode 308 when forming the third electrode502.

When the third conductor 502 is formed, the second insulation layer 311including the second contact hole 312 is formed as is shown in FIG. 13A.The second contact hole 312 is formed to overlap abridge a part of thefirst contact hole 310 and a part of the first insulation layer 309 thesame as in the first embodiment. However, unlike the first embodiment,the source electrode or drain electrode 308 is not exposed even if thesecond contact hole 312 is formed and instead the second conductor 501is exposed.

After the second insulation layer 311 is formed, the pixel electrode 313is formed next as is shown in FIG. 13B. The pixel electrode 313 can beformed from a transparent conductive material including at least oneselected from ITO, IZO and ZnO. In the present embodiment, the pixelelectrode 313 is also formed so as to cover the entire first contacthole 310 and a part of the second contact hole 312. Furthermore,although the pixel electrode 313 is formed so as to cover an end part ofthe second conductor 501 as is shown in FIG. 13B, the pixel electrode313 may also be formed so as to expose an end part.

As described above, according to the present embodiment, by arrangingthe third conductor 502 which functions as a capacitance electrode on alower part of the pixel electrode 313, it is possible to effectivelyutilize almost the entire region of a pixel as a capacitor. In addition,by arranging the second conductor 501 which functions as an etchantstopper on an upper part of the first contact hole 310 when forming suchas capacitor, it is possible to form the third conductor 502 withoutetching the source electrode or drain electrode 308.

Each embodiment of the present invention described above can be carriedout by an appropriate combination as long as they do not mutuallycontradict each other. In addition, a person ordinarily skilled in theart could appropriately add, remove or change the design of structuralelements or add, omit or change the conditions of processes based on theEL display device of each embodiment, as long as the gist of the presentinvention is provided, these are included in the scope of the presentinvention.

In addition, other operational effects different to the operationaleffects brought about by each embodiment described above, those that areobvious from the descriptions in the present specification or those thatcould be easily predicted by a person ordinarily skilled in the artshould also be interpreted as being brought about by the presentinvention.

What is claimed is:
 1. A display device comprising: a first conductor; afirst insulation layer including a first contact hole exposing a part ofthe first conductor; a second insulation layer including a secondcontact hole exposing at least a part of the first contact hole and apart of a surface of the first insulation layer; a pixel electrodeoverlapping a part of the second contact hole and electrically connectedto the first conductor; a third insulation layer contacting the firstinsulation layer via the second contact hole; and an EL layer includinga light emitting layer overlapping the pixel electrode, wherein an edgeof the second contact hole is in the first contact hole, and the thirdinsulation layer is between the pixel electrode and the EL layer.
 2. Thedisplay device according to claim 1, wherein the pixel electrode iselectrically connected to the first conductor via a second conductorcontacting the first conductor.
 3. The display device according to claim2, wherein the second conductor is formed from a material including atleast one selected from ITO, IZO and ZnO.
 4. The display deviceaccording to claim 1, wherein the second contact hole overlaps a part ofthe first contact hole in a planar view.
 5. The display device accordingto claim 1, wherein the first insulation layer and the third insulationlayer include a resin material and the second insulation layer includesan inorganic material.
 6. The display device according to claim 5,wherein the inorganic material includes silicon oxide or siliconnitride.
 7. The display device according to claim 1, wherein the firstconductor is a metal layer including at least one selected from Mo, Al,W and Cr, and the pixel electrode includes a transparent conductivelayer including at least one selected from ITO, IZO and ZnO.
 8. Thedisplay device according to claim 1, wherein the light emitting layer isfurther arranged within an aperture part exposing the pixel electrodearranged in the third insulation layer.
 9. The display device accordingto claim 1, wherein an edge of the pixel electrode is in the secondcontact hole.
 10. The display device according to claim 1, wherein thesecond insulation layer is arranged to extend from the inside of thefirst contact hole to the surface of the first insulation layer.
 11. Amethod of manufacturing a display device comprising: forming a firstconductor; forming a first insulation layer arranged with a firstcontact hole so as to expose a part of the first conductor; forming asecond insulation layer arranged with a second contact hole so as toexpose at least a part of the first contact hole and a part of a surfaceof the first insulation layer; forming a pixel electrode overlapping apart of the second contact hole and electrically connected to the firstconductor; forming a third insulation layer contacting the firstinsulation layer via the second contact hole; and forming an EL layerincluding a light emitting layer overlapping the pixel electrode,wherein an edge of the second contact hole is in the first contact hole,and the third insulation layer is between the pixel electrode and the ELlayer.
 12. The method of manufacturing a display device according toclaim 11 further comprising: forming a second conductor electricallyconnected to the first conductor so as to cover the entire first contacthole after forming the first contact hole; the pixel electrode beingelectrically connected to the first conductor via the second conductor.13. The method of manufacturing a display device according to claim 12,wherein the second conductor includes at least one selected from ITO,IZO and ZnO.
 14. The method of manufacturing a display device accordingto claim 11, wherein the second contact hole is formed so as to overlapa part of the first contact hole.
 15. The method of manufacturing adisplay device according to claim 11, wherein the first insulation layerand the third insulation layer include a resin material and the secondinsulation layer includes an inorganic material.
 16. The method ofmanufacturing a display device according to claim 15, wherein theinorganic material includes silicon oxide or silicon nitride.
 17. Themethod of manufacturing a display device according to claim 15, whereinthe first conductor is formed as a metal layer including at least oneselected from Mo, Al, W and Cr, and the pixel electrode is formed so asto include a transparent conductive layer including at least oneselected from ITO, IZO and ZnO.
 18. The method of manufacturing adisplay device according to claim 11, wherein an aperture part exposingthe pixel electrode is formed in the third insulation layer, and thelight emitting layer is further formed within the aperture part.
 19. Themethod of manufacturing a display device according to claim 11, whereinan edge of the pixel electrode is in the second contact hole.
 20. Themethod of manufacturing a display device according to claim 11, whereinthe second insulation layer is arranged to extend from the inside of thefirst contact hole to the surface of the first insulation layer.